1. Technical Field
The present invention relates to a terminal for coaxial cable for connecting a coaxial cable (coaxial cable to be used for an automobile glass antenna for example) to a circuit element on a base board (an antenna element on the surface of a glass board for example) and the like, and an attachment structure and an attachment method for attaching the same terminal for coaxial cable to a base board (an automobile glass board for example) and the like.
2. Prior Art
In case of connecting an end portion of a coaxial cable for transmitting a high-frequency signal with a base board, it is necessary to strip off coverings of the end portion of the coaxial cable and to connect a center conductor and an outer conductor respectively to specified portions of a circuit element on the base board.
Up to now, in case of attaching such an end portion of a coaxial cable directly to a circuit on a base board, a terminal for coaxial cable 31 as shown in FIG. 11 for example is used.
This terminal for coaxial cable 31 is formed by pressing and then bending a conductive plate material 31a, and is attached to a covering-stripped end portion 30A of a coaxial cable 30.
The terminal for coaxial cable 31 is formed so as to be nearly bilaterally symmetrical with respect to the axial line of the coaxial cable 30 and has a barrel portion 33 for clamping a folded-back portion 32A of a meshed wire of an outer conductor 32 at its rear portion, and this barrel portion 33 is composed of a pair of left and right clamping pieces 33A and 33B, both clamping pieces 33A and 33B being opened downward in an inverted U-shape in FIG. 11 in a state where the outer conductor 32 is not clamped.
An intrusive portion 34 is protruded inside the barrel portion 33 in the middle of the base parts of both clamping pieces 33A and 33B, and this intrusive portion 34 intrudes into the meshed wire of the outer conductor 32 to suppress the backward slippage in position of the coaxial cable 30.
And the terminal for coaxial cable 31 is attached to an end portion of the coaxial cable 30 by inserting and clamping the end portion of the coaxial cable 30 into the barrel portion 33 so that the fore-end edge of the folded-back portion 30A of the coaxial cable 30 does not touch the intrusive portion 34 by means of the clamping pieces 33A and 33B.
In such a way, after the terminal for coaxial cable 31 has been attached to the end portion of the coaxial cable 30, the outer conductor 32 is connected to a contact portion 38 by fitting a leg 35 of the terminal for coaxial cable 31 into a fitting hole 37 of a printed wiring board 36 and soldering the fore-end portion of the leg 35 at the reverse face side of the printed wiring board 36. The center conductor 39 of the coaxial cable 30 is soldered to a contact portion 36A of the printed wiring board 36 (see Patent Literature 1: Japanese Patent Laid-Open Publication No. 2000-323,213).
And FIG. 12 shows another prior art as a coaxial cable connection structure for connecting a coaxial cable to a printed wiring board.
This coaxial cable connection structure provides a printed wiring board 40 with a slit 41, forms a strip line 42 on the extension of this slit 41, forms a grounding pattern 43 at both sides of the slit 41, fits an outer conductor 45 of a coaxial cable 44 in the slit 41, solders a center conductor 46 to the strip line 42 and solders the outer conductor 45 to the grounding pattern 43, holds down the outer conductor 45 with a cable clamp 47, and fixes this cable clamp 47 on the printed wiring board 40 (see Patent Literature 2: Japanese Patent Laid-Open Publication No. 2003-168,499).
For example, in a terminal for coaxial cable for connecting a coaxial cable to be used for an automobile glass antenna to an antenna element on the surface of an automobile glass board, it is very important to control the position of attachment of the terminal for coaxial cable.
That is to say, it is necessary not only to stably attach a center conductor and an outer conductor of the fore-end portion of a coaxial cable respectively to the same positions as determined in a terminal for coaxial cable but also to accurately and stably attach the center conductor and the outer conductor in position of attachment at a specified interval on a mounted object.
In a terminal for coaxial cable of the former prior art as described above, however, since a coaxial cable 30 is in a state where only an outer conductor 32 of it is fixed to the terminal for coaxial cable 31, there has been a problem that it is difficult to stably attach the center conductor and the outer conductor of the fore-end portion of the coaxial cable 30 respectively to the same positions as determined on a base board and to accurately and stably attach the center conductor and the outer conductor to the same positions as determined with respect to the interval between them.
And since the outer conductor 32 is connected to the contact portion 38 by clamping the folded-back portion 32A of a meshed wire being the outer conductor 32 of the coaxial cable 30 with the clamping pieces 33A and 33B of the barrel portion 33 of the terminal for coaxial cable 31, fitting the leg 35 in the fitting hole 37 of the printed wiring board 36, and soldering the fore-end portion of the leg 35 at the reverse face side of the base board 36, the coaxial cable 30 is in a state where only its outer conductor 32 is fixed to the terminal for coaxial cable 31. Due to this, there has been a problem that in case that a load is applied to the coaxial cable 30 particularly in a period from a time when the coaxial cable has been press-joined to a time when the mounting is finished by soldering an element on the base board, the whole load applied to the coaxial cable 30 is applied to the barrel portion 33 being the press-joined portion and thereby the barrel portion 33 is broken.
Also in case of using a coaxial cable connection structure of the latter prior art as described above for an automobile glass antenna, there has been a problem that it is difficult to stably attach the center conductor and the outer conductor of the fore-end portion of a coaxial cable respectively to the same positions as determined and to accurately and stably attach the center conductor and the outer conductor to the same positions as determined with respect to the interval between them.
And due to soldering the center conductor 46 of a coaxial cable 44 to a strip line 42, soldering the outer conductor 45 to a grounding pattern 43, holding down the outer conductor 45 with a cable clamp 47, and fixing this cable clamp 47 to a printed wiring board 40, there has been a problem that in case that a load is applied to the coaxial cable 44, the whole load applied to the coaxial cable 44 is applied to the cable clamp 47 and thereby the cable clamp 47 or the coaxial cable 44 is broken. Using a terminal for coaxial cable having a housing of insulator is also conceivable but is disadvantageous for miniaturization.
And there has been a problem that a hole or a slit must be provided in a printed wiring board. For example, in case of using such a terminal for coaxial cable for an antenna element on the surface of an automobile glass board, there has been a problem of being unable to make a hole in the board and solder on the reverse face or provide a slit.
The present invention has been performed in order to solve the above-described problems, and a first object of the invention is to provide a terminal for coaxial cable making it possible to stably attach a center conductor and an outer conductor of the fore-end portion of a coaxial cable respectively to the same positions as determined, accurately and stably attach the center conductor and the outer conductor to the same positions as determined on a mounted object also with respect to the interval between them, reduce a load applied to cable connection portions (a center conductor press-joined portion and an outer conductor press-joined portion) in a period from a time when the center conductor and the outer conductor have been press-joined to a time when the mounting is finished by soldering an element on the board and prevent the cable connection portion from being broken, said terminal for coaxial cable having no need for providing a hole or a slit in the printed wiring board.
And a second object of the invention is to provide an attachment structure of a terminal for coaxial cable making it possible to stably attach a center conductor and an outer conductor respectively to the same positions as determined on a mounted object (for example, an antenna element on the surface of an automobile glass board), accurately and stably attach the center conductor and the outer conductor to the same positions as determined also with respect to the interval between them, reduce a load to be applied to the cable connection portion (center conductor press-joined portion and outer conductor press-joined portion) in a period from a time when the center conductor and the outer conductor have been press-joined to a time when the mounting is finished by soldering an element on the board and prevent the cable connection portion from being broken, said terminal for coaxial cable having no need for providing a hole or a slit in the printed wiring board.
And a third object of the invention is to provide a method for attaching a terminal for coaxial cable making it possible to stably attach a center conductor and an outer conductor respectively to the same positions as determined on a mounted object (for example, an antenna element on the surface of an automobile glass board), accurately and stably attach the center conductor and the outer conductor to the same positions as determined with respect to the interval between them, reduce a load applied to cable connection portions (a center conductor press-joined portion and an outer conductor press-joined portion) in a period from a time when the center conductor and the outer conductor have been press-joined to a time when the mounting is finished by soldering an element on the board and prevent the cable connection portion from being broken, said terminal for coaxial cable having no need for providing a hole or a slit in the printed wiring board.